Packoff Sealing Assembly

ABSTRACT

A packoff assembly for sealing a space between an inner well member and an outer well member. The packoff assembly has a packoff body, and a sealing mechanism with a U-shaped cross-section, including a packoff body leg and a well component leg extending substantially downward from a transverse connecting section. The well component leg is elastically bendable so that it resists inward deflection toward the packoff body and so that the sealing mechanism can be set without the use of an energizing ring. The packoff body leg is configured for engagement with the packoff body, and the well component leg has a sealing surface configured for sealing engagement with the inner or the outer well member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This technology relates to oil and gas wells, and in particular to sealing mechanisms in packoff assemblies for use in oil and gas wells.

2. Brief Description of Related Art

Typical oil and gas wells have a wellhead. Strings of casing, each supported by a casing hanger, are lowered into the wellhead. Typically, the casing hanger is threaded, and is attached to a threaded upper end of the casing string. The casing hanger lands on a landing shoulder in the wellhead, or alternatively, may land on a previously installed casing hanger having a larger diameter. With the casing string in place, cement may be pumped down the casing until it comes back up the annulus around the casing. After the cement is pumped, a packoff assembly may be positioned between the wellhead and an upper portion of the casing hanger to seal the casing hanger annulus.

Some older wellheads include packoff seals that are elastomeric, and that don't include any form of anti-extrusion device. Furthermore, many older oil wells are now being extended past the original design life of such packoff seals, and some are experiencing long term gas migration out to the larger diameter annuli, such as those where the packoff seals are located. In addition, this older equipment has often been in use for long periods of time, and drilling operation damage to surfaces of the wellhead and/or the casing hanger is possible. The packoff seals originally installed in the wells are often not suitable for overcoming these problems. For example, elastomeric seals are susceptible to degradation in their mechanical properties over time. Thus, as the life of the well becomes extended, the packoff seal may not be reliable.

Attempts have been made to fix the problems associated with such older, inadequate packoff seals. In some instances, such seals have been replaced with newer flouroelastomer or elastomeric seal elements incorporating anti-extrusion devices. However, replacement and reinstallation of the packoff seals can be complicated, requiring the use of complex running tools and procedures. Furthermore, elastomeric seals are still subject to degradation when exposed to high pressure and temperature in the well. In addition, because surfaces of the well components may be damaged, achieving an adequate seal with a replacement packoff sealing assembly can be difficult.

SUMMARY OF THE INVENTION

Disclosed herein is a packoff assembly for sealing the space between an inner well member and an outer well member when the packoff assembly is inserted therebetween. In some embodiments, the inner and outer well members may be a casing hanger and a wellhead, respectively. The packoff assembly includes a packoff body and a sealing mechanism. The sealing mechanism has an annular shape with a U-shaped cross-section that has a packoff body leg and a well component leg extending downward from a connecting section.

The well component leg has a sealing surface that can seal against surfaces of the well members. In addition, the well component leg is elastically bendable so that it resists inward deflection toward the packoff body, and so that the sealing mechanism can be set without the use of an energizing ring. The packoff body leg may be configured for engagement with the packoff body. Alternatively, the packoff body leg may be integral to the packoff body.

If the sealing mechanism is positioned on the inside of the packoff body, the sealing surface seals against the inner well member, which may be a casing hanger. Conversely, if the sealing mechanism is positioned outside the packoff body, the sealing surface seals against the outer well member, which may be a wellhead. In some embodiments, a sealing mechanism may be located on both the inside and the outside of the packoff body. The sealing mechanism may further include an inlay positioned on an outer surface of the well component leg, and configured to engage and seal against the well member when the sealing mechanism is positioned between the packoff body and the well member. One purpose of the inlay is to conform to imperfect or damaged surfaces of well components so that the sealing mechanism can form a tight seal with such surfaces.

Also disclosed herein are additional features of the packoff assembly. For example, wiper rings may be attached to the packoff body below the sealing mechanisms to wipe the surfaces of the inner and outer well members as the packoff assembly is installed, thereby preparing the surfaces for sealing engagement with the sealing mechanisms. In addition, upper seals may be installed on the packoff body above the sealing mechanisms to shield the sealing mechanisms from pressures above the packoff assembly. Furthermore, a retainer plate may be connected to the bottom of the packoff body to retain the sealing mechanisms and wiper rings in place relative to the packoff body.

BRIEF DESCRIPTION OF THE DRAWINGS

The present technology will be better understood on reading the following detailed description of nonlimiting embodiments thereof, and on examining the accompanying drawings, in which:

FIG. 1 is a perspective view of a sealing mechanism according to an embodiment of the present technology;

FIG. 2 is an enlarged sectional view of a packoff assembly including the sealing mechanism shown in FIG. 1:

FIG. 3 is a schematic cross-sectional view of a packoff assembly including the sealing mechanism of the present technology, with the packoff assembly inserted between a well head and a casing hanger;

FIG. 3A is an enlarged schematic cross-sectional view of the portion of the packoff assembly identified by area 3A in FIG. 3;

FIG. 4 is a schematic sectional view of the sealing mechanism of the present technology and including an inlay; and

FIG. 4A is an enlarged cross-sectional view of the portion of the sealing mechanism identified by area 4A in FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The foregoing aspects, features, and advantages of the present technology will be further appreciated when considered with reference to the following description of preferred embodiments and accompanying drawings, wherein like reference numerals represent like elements. In describing the preferred embodiments of the technology illustrated in the appended drawings, specific terminology will be used for the sake of clarity. However, the technology is not intended to be limited to the specific terms used, and it is to be understood that each specific term includes equivalents that operate in a similar manner to accomplish a similar purpose.

FIG. 1 is a perspective view of a portion of a sealing mechanism 10. The sealing mechanism 10 is an annularly shaped ring that has a U-shaped cross section 12, including a packoff body leg 14 and a well component leg 16. The legs 14, 16 are attached to, and extend downwardly from, a connecting section 17. In certain embodiments, the sealing mechanism 10 is made of metal, and the packoff and well component legs 14, 16 are sufficiently stiff to resist inward deflection. The outer, lower surface of the well component leg 16 is a sealing surface 18, configured to sealingly engage a surface of a well component, as described in detail below. In the embodiment shown, the sealing surface 18 extends radially outward beyond the upper portion of the well component leg 16. The sealing mechanism may be made of metal.

Referring now to FIG. 2, a packoff assembly 19 is shown, including a pair of sealing mechanisms 10, which are shown installed on a packoff body 20 configured for insertion between well components, such as, for example, a casing hanger 22 and a wellhead 24 (shown in FIG. 3). As shown, the sealing mechanisms 10 may be positioned so that the packoff body leg 14 is positioned toward the packoff body 20. The packoff body leg 14 may be attached to the packoff body 20 by any appropriate means. The well component leg 16, including the sealing surface 18, is positioned away from the packoff body 20. Alternatively, the sealing mechanism 10 may be integral to the packoff body 20. In such an embodiment, the packoff body leg 14 may be omitted from the sealing mechanism 10, and the connecting section 17 may connect the well component leg 16 directly to the packoff body 20.

In addition to the sealing mechanisms 10, the packoff assembly 19 includes wiper rings 28, upper and lower retainer spacers 30, 32, upper packoff seals 34, and a retainer plate 36. The purpose of the wiper rings 28 is to wipe and clean the surfaces of the well components during installation of the packoff body 20, as described in further detail below. The wiper rings 28 may be made of any suitable material. For example, in some embodiments, the wiper rings may be made of polytetraflouroethylene. The purpose of the upper and lower retainer spacers 30, 32 is to maintain the position of the sealing mechanisms 10 and the wiper rings 28 relative to the packoff body 20 and each other. The purpose of the upper packoff seals 34 is to provide an upstream seal between the packoff body 20 and adjacent well components above the sealing mechanisms 10. Such an upstream seal may be beneficial, for example, to isolate the sealing mechanisms 10 from connection void test pressure or other upstream pressure.

Retainer plate 36 may be positioned below the sealing mechanisms 10, upper and lower retainer spacers 30, 32, and wiper rings 28, and maintains these elements in place relative to the packoff body 20. To accomplish this, the retainer plate 36 protrudes radially beyond the lower end 38 of the packoff body 20 a distance sufficient to restrict downward movement of the sealing mechanisms 10, upper and lower retainer spacers 30, 32, and wiper rings 28 relative to the packoff body 20. The retainer plate 36 may be releasably attached to the packoff body 20 by, for example, a fastener 40. Fastener 40 may optionally be a bolt that threads into a corresponding recess 42 in the lower end 38 of the packoff body 20. The ability to release the retainer plate 36 from the packoff body 20 is advantageous because it allows the removal and replacement of the sealing mechanisms 10, upper and lower retainer spacers 30, 32, and wiper rings 28.

The packoff assembly 19 shown in FIG. 2 has the sealing mechanisms 10, upper and lower retainer spacers 30, 32, and wiper rings 28 installed on both inside and outside surfaces of the packoff body 20. Such an embodiment is beneficial for forming a seal between the packoff body 20 and multiple well components (such as the casing hanger 22 and wellhead 24 shown in FIG. 3). Alternatively, however, some embodiments may include only a single sealing mechanism 10, upper and lower retainer spacer 30, 32, and wiper spacer 28. In such an embodiment, these components may be mounted either on the outside surface 44 or the inside surface 46 of the packoff body 20. In any configuration, the packoff body leg 14 of the sealing mechanism 10 will be located adjacent to, and may engage, the packoff body 20. In addition, the well component leg 16, including the sealing surface 18, will be located away from the packoff body 20.

FIG. 3 shows the packoff assembly 19 inserted between a casing hanger 22 and a wellhead 24 to seal the space between the casing hanger 22 and the wellhead 24. A method of assembling and installing the packoff assembly 19 is described herein, and includes, prior to insertion, assembly of the packoff assembly 19. In embodiments having an upper retainer spacer 30, such as that shown in FIG. 3, the upper retainer spacer 30 is moved into place relative to the packoff body 20. Thereafter, in embodiments where the sealing mechanism 10 is not integral to the packoff body 20, the sealing mechanism 10 may be inserted onto the surface of the packoff body 20. After the sealing mechanism 10 is installed on the packoff body 20, the lower retainer spacer 32 and wiper ring 28 are moved into place relative to the packoff body 20. Thereafter, the retainer plate 36 is attached to the lower end 38 of the packoff body 20, thereby retaining the sealing mechanism 10, upper and lower retainer spacers 30, 32, and wiper ring 28 in place relative to the packoff body 20.

With the packoff assembly 19 thus assembled, it is ready for installation between well components, such as the casing hanger 22 and the wellhead 24. To accomplish this, the packoff assembly 19 is run through a pressure management device (not shown), such as a blowout preventer, attached to the top of the well. From the pressure management device, the packoff assembly 19 is inserted into the space between the well components. During insertion, the wiper rings 28, which are positioned below the sealing mechanisms 10, wipe the surfaces of the well components, in order to remove debris and otherwise clean the surfaces. This is beneficial to provide better sealing between the surfaces of the well components and the sealing surfaces 18 of the sealing mechanisms 10 when the packoff assembly 19 is in place.

In the embodiment shown, after insertion, the packoff assembly 19 is locked axially in place by a lock down screw 48. The lock down screw 48 may pass through the wellhead 24 and engage a groove 50 in the packoff body 20, thereby restricting axial movement of the packoff assembly 19 relative to the wellhead 24. Alternate embodiments may provide different means of locking the packoff assembly 19 axially in place, and use of a lock down screw 48 is not required. For example, another embodiment might include an internal lock down ring (not shown) inserted above the packoff assembly 19 to prevent upward axial movement.

As best shown in FIG. 3A, upon insertion, the sealing surface 18 of the well component leg 16 contacts the surfaces of the well components, such as the casing hanger 22 or the wellhead 24. The sealing surface 18 extends radially outward beyond the upper portion of the well component leg 16, and, when the well component leg 16 is in an undeflected state, is arranged in a conical configuration around the sealing mechanism 10. Upon further insertion and seating of the sealing mechanism 10, however, the well component leg 16 is deflected toward the packoff body 20. As the well component leg 16 is deflected toward the packoff body 20, the sealing surface 18 shifts to a cylindrical configuration around the sealing mechanism 10. The sealing mechanism 10 is preferably an elastic seal. Accordingly, although the well component leg 16 deflects upon insertion of the packoff assembly 19, it regains its original undeflected configuration upon removal of the sealing mechanism 10 from between the well components. Furthermore, the elasticity of the sealing mechanism 10 allows for insertion and setting of the sealing mechanism 10 without an energizing ring.

In one embodiment, the magnitude of the stiffness of the well component legs 16 allows deflection of the well component leg 16 and setting of the seal 10 with a relatively low set weight. For example, the set weight may be 25,000 pounds or less. Such a low set weight allows use of the seals in surface wellhead applications, and, in particular, large diameter casing annuli. In addition, because the sealing mechanism 10 is weight set, only a simple running tool is required for installation.

Because the well component legs 16 are stiff, the inward deflection of the well component legs 16 is resisted by a resistive force F. The resistive force F is constantly maintained as long as the packoff assembly 20 is in place and the well component leg 16 of the sealing mechanism 10 is deflected inward toward the packoff body 20. In addition, the resistive force F pushes the sealing surfaces 18 against the well components. Thus, a seal is formed between the sealing surfaces 18 and the well components. Because the sealing surfaces 18 of the sealing mechanism 10 are metal, and the surfaces of the well components are metal, the seal formed therebetween is a metal-to-metal seal. Thus, the seal is capable of withstanding higher pressures and temperatures than elastomeric or other types of seals.

Referring to FIGS. 4 and 4A, there is shown an embodiment of the present technology that includes an inlay 52. The inlay 52 may be made of a metal that is softer than the metal of the well components. In one example embodiment, the inlay 52 is made of annealed silver. As shown in FIGS. 4 and 4A, the inlay 52 may be attached to the well component leg 16 of the sealing mechanism 10. In such an embodiment, the well component leg 16 of the sealing mechanism 10 has grooves 54, which may be located on the sealing surface 18 of the well component leg 16. Prior to insertion of the packoff assembly 19 into the space between the well components, the inlay 52 may be attached to the sealing surface 18 of the well component leg 16 by soldering, or other appropriate means.

Thereafter, upon insertion of the packoff assembly 19 between the well components, as described above, the inlay 52 is compressed between the sealing surface 18 of the sealing mechanism 10 and the surface of a well component. Because the inlay 52 is made of a metal that is softer than the metal of the well component, the resistive force F (shown in FIG. 3A) that pushes the sealing surface 18 into the surface of the well component causes the inlay 52 to deform until it matches the contour of the surface of the well component. This feature is advantageous because it improves the seal between the sealing mechanism 10 and the well component, particularly where the surfaces of the well component are not smooth, have been damaged during operations, or otherwise have defects that would prevent an effective seal. Thus, the sealing mechanism 10 is suitable for use in retrofit applications, such as where a casing is leaking due to old or inadequate packoff sealing, and a more sure seal is needed. In addition to the seal created between the inlay 52 and the well component, the portion of the sealing surface 18 below the inlay 52 may also contact and seal against surfaces of the well component.

While the technology has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention. Furthermore, it is to be understood that the above disclosed embodiments are merely illustrative of the principles and applications of the present invention. Accordingly, numerous modifications may be made to the illustrative embodiments and other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. 

What is claimed is:
 1. A packoff assembly for sealing a space between an inner well member and an outer well member, the packoff assembly comprising: a packoff body configured for insertion between the inner well member and the outer well member; and a sealing mechanism for scaling between the packoff body and the inner or outer well member, the sealing mechanism having a U-shaped cross-section including a packoff body leg and a well component leg extending substantially downward from a transverse connecting section, the well component leg having a sealing surface configured for sealing engagement with the inner or outer well member, the well component leg being elastically bendable so that it resists inward deflection toward the packoff body and so that the sealing mechanism can be set without the use of an energizing ring.
 2. The packoff body of claim 1, wherein the sealing mechanism further comprises an inlay positioned on the sealing surface of the well component leg, and configured to sealingly engage the inner or outer well member.
 3. The packoff assembly of claim 1, wherein the packoff body leg is separate from, and configured for positioning adjacent to, the packoff body.
 4. The packoff assembly of claim 1, wherein the packoff body leg is integral with the packoff body.
 5. The packoff assembly of claim 1, wherein the inner well member is a casing hanger.
 6. The packoff assembly of claim 1, wherein the outer well member is a wellhead.
 7. The packoff assembly of claim 1, wherein the sealing mechanism is composed of metal.
 8. The packoff assembly of claim 2, wherein the inlay is made of a metal that is softer than the metal of the well members so that as the well component leg seals against the well member, the inlay deforms to conform to the surface of the well member.
 9. The packoff assembly of claim 1, wherein the well component leg is positioned so that the sealing surfaces are conically shaped when the packoff assembly is not installed between the inner and outer well members.
 10. The packoff assembly of claim 1, wherein the well component leg is positioned to that the sealing surfaces are cylindrically shaped when the packoff assembly is installed between the inner and outer well members and the sealing surfaces are engaged with the inner or outer well member.
 11. The packoff body of claim 2, wherein the inlay is soldered onto the surface of the well component leg of the sealing mechanism.
 12. A seal assembly for sealing a space between an inner well member and an outer well member, the seal assembly comprising: a packoff body; a pair of seals configured for positioning between the packoff body and the inner and outer well members, the seals having U-shaped cross-sections, each with a packoff body leg and a well component leg extending downwardly from a transverse connecting section, the well component legs of the seals being elastically bendable so as to resist inward deflection toward the packoff body, and to enable the seals to be set without the use of an energizing ring; the packoff body legs configured to threadedly engage the packoff body; and the well component legs having a sealing surface configured to mate with, and seal against, the sealing surface of the inner or outer well component.
 13. The seal assembly of claim 12, wherein each seal further comprises an inlay that is softer than the well members and that is attached to the well component legs, so that as the sealing surface of each well component leg seals against the sealing surface of the well component, the inlay deforms to conform to the surface of the well component, thereby strengthening the seal between the well component leg and the well component.
 14. The seal assembly of claim 12, further comprising: wiper rings installed on the packoff body below the pair of seals to clear debris from the well members as the packoff body and seals are positioned relative to the well members.
 15. The seal assembly of claim 12, further comprising: upper seals positioned above the pair of seals to form an additional upper seal between the packoff body and the well members, and to isolate the pair of seals from pressure above the upper seals.
 16. The seal assembly of claim 12, wherein the inner well member is a casing hanger.
 17. The seal assembly of claim 12, wherein the outer well member is a wellhead.
 18. The seal assembly of claim 12, wherein the pair of seals are composed of metal.
 19. The seal assembly of claim 13, wherein the inlay is composed of annealed silver.
 20. A seal assembly for sealing the space between a wellhead and a casing hanger, the sealing assembly comprising: a packoff body configured for insertion between the wellhead and the casing hanger; a pair of annular metal seals for sealing between the packoff body and the wellhead and casing hanger, the pair of annular metal seals each having a U-shaped cross-section including a packoff body leg and a well component leg extending substantially downward from a transverse connecting section, the well component leg having a sealing surface configured for sealing engagement with the wellhead or the casing hanger, the well component leg being elastically bendable so that it resists inward deflection toward the packoff body and so that the pair of annular metal seals can be set without the use of an energizing ring; a pair of wiper rings attached to the packoff body below the pair of annular metal seals and configured to contact and wipe clean the surfaces of the wellhead and the casing hanger as the seal assembly is inserted therebetween; a retainer plate attached to the bottom of the packoff body and extending radially outward therefrom to retain the position of the pair of annular metal seals and the pair of wiper rings relative to the packoff body; and a pair of upper elastomeric seals positioned above the annular metal seals and configured to seal between the packoff body and the wellhead and casing hanger and to isolate the pair of seals from pressure above the upper seals. 